Why the first Ekadasi has got such a superiority ?

We know the Ekadasi Tidhi is more than a festival day

 for the religious worship as Vratam.

 It is a Spiritual merit for every Hindu.

It is said, the Ekadasi Vratam should be done like this,

 as one has to take one time meal at noon before the

 Ekadasi tidhi (means Dasami day) and next on Ekadasi day

 he should do the fasting and next day  on Dwadasi ,

he should do all the religious deeds and offer the

 food to any worthy person , who is a guest like a  

Sree Maha Vishnu  and then he has to take his food . 

In every month the Ekadasi tidhi comes twice. 

Ashadha Sukla Paksha Ekadasi is called as the first Ekadasi (Pradhama)

On this first Ekadasi day, Lord Sree Mannarayana

takes His Yoga Nidra . 

Means, Lord Sree Mahavishnu

after the destruction of the world sleeps for certain period

which is a state of supernatural sleep attained by a Yogi.

The Lord sleeps for four months. 

Till Kkartika Sukla Ekadasi day,

 he will be in the Yoga Nidra.