CSS

Placeholder font-family

.mainLoginInput::placeholder { /* Chrome, Firefox, Opera, Safari 10.1+ */
  font-family: 'myFont', Arial, Helvetica, sans-serif;
  opacity: 1; /* Firefox */
}

.mainLoginInput:-ms-input-placeholder { /* Internet Explorer 10-11 */
  font-family: 'myFont', Arial, Helvetica, sans-serif;
}

.mainLoginInput::-ms-input-placeholder { /* Microsoft Edge */
  font-family: 'myFont', Arial, Helvetica, sans-serif;
}

/*Other variants that might work*/
.mainLoginInput::-webkit-input-placeholder {
  font-family: 'myFont', Arial, Helvetica, sans-serif;
}

.mainLoginInput:-ms-input-placeholder {
  font-family: 'myFont', Arial, Helvetica, sans-serif;
}

.mainLoginInput:-moz-placeholder {
  font-family: 'myFont', Arial, Helvetica, sans-serif;
}

.mainLoginInput::-moz-placeholder {
  font-family: 'myFont', Arial, Helvetica, sans-serif;
}